The invention concerns a manufacturing method of plastic bonded electrodes for electrochemical power sources, such as batteries, wherein the plates have a controlled porosity. The manufacturing method includes a rolling step.
The rolling method of the invention is suitable for the manufacture of porous electrodes of batteries, especially for cadmium electrodes for alkaline batteries.
In the known methods for manufacturing such electrodes and plates, the active mass for the electrode is either enclosed in a perforated steel pocket or it is deposited in pores of a porous nickel body. In the first case the starting products for the manufacturing method is a prepressed longish rectangular briquette which is prepared by pressing the active mass; such briquettes are subsequently enclosed in perforated steel pockets that are thereafter coupled by welding to assume the form of electrododes of a desired shape. In the second case a porous nickel body, prepared by sintering a nickel powder, is several times impregnated by salt solutions of the electrochemically active metals which are subsequently precipitated in the form of hydroxides or oxides.
Further methods for preparing electrodes of the aforedescribed types are known from the literature. For example, in the method described in U.S. Pat. No. 3,009,980 (Nov. 21, 1961) a layer of a pasty active mass is deposited on the current collector by dipping; the liquid is removed by drying and the resulting semi-finished product is further treated by rolling.
A high labor consumption and the difficulty in attaining an optimum porous structure due to the use of a pasty active mass constitute important disadvantages of this known method.
A further known method (described in German Patent No. 1,187,698) for preparing plastic bonded electrodes, uses an electrochemically active material and two different resins. One of the resins serves as a pore forming agent which is removed by dissolving it after the electrode has been formed.
The main disadvantages of the last described known manufacturing method are the large labor consumption which is required and the necessity of extracting one resin from the electrode body.
The afore-described manufacturing methods, as described in the literature of the state of the art, are therefore not used in the mass production of electrodes of the aforedescribed type.